In the disclosure of the present invention reference is mostly made to drug delivery devices, such devices being used e.g. in the treatment of diabetes, however, this is only an exemplary use of the present invention.
Drug injection devices have greatly improved the lives of patients who must self-administer drugs and biological agents. Drug injection devices may take many forms, including simple disposable devices that are little more than an ampoule with an injection means or they may be durable devices adapted to be used with pre-filled cartridges. Regardless of their form and type, they have proven to be great aids in assisting patients to self-administer injectable drugs and biological agents. They also greatly assist care givers in administering injectable medicines to those incapable of performing self-injections.
The typical diabetes patient will require injections of insulin several times during the course of a week or a day. For other types of drug the intervals between drug deliveries may be shorter or longer. However, typical injection devices do not address the problem of a user not remembering when the last injection was administered.
Even shortly after administering a dose of insulin, the user now and then will be in doubt as to whether he actually carried out an injection or not. This could be after minutes or even hours after the intended time for performing an administration. Thus, there exist the potential hazard that the patient chooses not to take his or her medication or that it is taken twice.
Some prior art devices, such as the electronic drug delivery device disclosed in WO 97/30742, are provided with an electronic monitoring system adapted to automatically start an electronic timer when a selected dose is expelled and to show the progress in time on an electronic display. Such an injection device generally provides a satisfactorily solution to the problem addressed above. However, for simpler devices such as disposable drug delivery devices, i.e. so-called pre-filled devices, the incorporation of this kind of electronics would normally not be economically viable. In addition, such a solution may not be environmentally acceptable due to the potential increase in the disposal of electronic components.
Addressing this issue, U.S. Pat. No. 8,743,662 discloses a cap-formed electronic timer device which is intended to be used with pre-filled drug delivery devices of the pen-type to replace the standard cap. The cap comprises a switch mechanism adapted to detect when the cap is placed on the delivery device, and released when the cap is removed from the dosing device, the engagement and/or releasing of the switch mechanism causing the timer unit to reset (preferably with a delay of some seconds), the time since the timer unit was last reset thereby indicating the time that has elapsed since the cap was removed, this again indicating when the drug delivery likely was used to deliver a dose of drug. This functionality is often termed “time-since-last-dose”. The cap is provided with a non-replaceable power source, e.g. a button cell.
Using the same form factor U.S. Pat. No. 8,817,258 discloses a cap-device which is adapted to measure the amount of drug remaining in the cartridge and thereby to create a log of dose amounts expelled from the cartridge between two measurements. Addressing the issue of detecting the size of an expelled amount of drug WO 2014/161952 discloses a ring-formed add-on device adapted to be mounted on the body portion of a drug delivery device, the device being turned on and off when the cap is removed and reattached.
A cap-formed electronic add-on device to be used in combination with a handheld drug delivery device has also been proposed in the form of a blood glucose meter (BGM), see e.g. WO 2012/152628.
To register use of the pen device, the add-on device may be provided with a powered switch which needs to change state to detect a cap-on/cap-off event. For example, to prevent power consumption after manufacturing and during storage prior to use when the cap is mounted on a pen device for the first time (shelf life), the powered switch may be open during storage. However, this means that the switch is open during use of the pen device and closed between uses of the device. As the latter state represents most of the use time for the add-on device this is power-costly. Alternatively, a powered switch may be closed when it is off the pen and open when it is mounted on the pen, however, this would be power-costly during storage. In the present context a powered switch defines a switch in which an electric potential is applied across the switch, this allowing a current to flow when the switch is in a closed state and prevents (apart from any leak current) a current to flow when the switch is in an open state.
EP 1 354 609 discloses a jet injector device having a suction pump which can enter a low-power sleeping mode to save energy.
Having regard to the above, it is an object of the present invention to provide an electronic add-on device to be used in combination with a receiving device, and which is both user-friendly and power-efficient during its entire life-time, such an arrangement being relevant for any electronic device having a use-scenario of the type described above. It is a further object to provide such a device in the form of a cap-device to be used in combination with a drug delivery device and which at least in part is controlled when the cap is removed and reattached to the device.